Re: [PATCH UPDATE] deflate stack usage in lib/inflate.c

Matt Mackall
2007-04-13T18:55:48Z

On Thu, Apr 12, 2007 at 01:50:54PM -0700, Jeremy Fitzhardinge wrote:
> Subject: deflate stack usage in lib/inflate.c
>
> inflate_fixed and huft_build together use around 2.7k of stack. When
> using 4k stacks, I saw stack overflows from interrupts arriving while
> unpacking the root initrd:
>
> do_IRQ: stack overflow: 384
> [<c0106b64>] show_trace_log_lvl+0x1a/0x30
> [<c01075e6>] show_trace+0x12/0x14
> [<c010763f>] dump_stack+0x16/0x18
> [<c0107ca4>] do_IRQ+0x6d/0xd9
> [<c010202b>] xen_evtchn_do_upcall+0x6e/0xa2
> [<c0106781>] xen_hypervisor_callback+0x25/0x2c
> [<c010116c>] xen_restore_fl+0x27/0x29
> [<c0330f63>] _spin_unlock_irqrestore+0x4a/0x50
> [<c0117aab>] change_page_attr+0x577/0x584
> [<c0117b45>] kernel_map_pages+0x8d/0xb4
> [<c016a314>] cache_alloc_refill+0x53f/0x632
> [<c016a6c2>] __kmalloc+0xc1/0x10d
> [<c0463d34>] malloc+0x10/0x12
> [<c04641c1>] huft_build+0x2a7/0x5fa
> [<c04645a5>] inflate_fixed+0x91/0x136
> [<c04657e2>] unpack_to_rootfs+0x5f2/0x8c1
> [<c0465acf>] populate_rootfs+0x1e/0xe4
>
> (This was under Xen, but there's no reason it couldn't happen on bare
> hardware.)
>
> This patch mallocs the local variables, thereby reducing the stack
> usage to sane levels.
>
> Also, up the heap size for the kernel decompressor to deal with the
> extra allocation.

Lost the non-x86 bits again.

--
Mathematics is the supreme nostalgia of our time.